Goldman Sachs analysts attempted to address a touchy subject for biotech companies, especially those involved in the pioneering "gene therapy" treatment: cures could be bad for business in the long run.

"Is curing patients a sustainable business model?" analysts ask in an April 10 report entitled "The Genome Revolution."

"The potential to deliver 'one shot cures' is one of the most attractive aspects of gene therapy, genetically-engineered cell therapy and gene editing. However, such treatments offer a very different outlook with regard to recurring revenue versus chronic therapies," analyst Salveen Richter wrote in the note to clients Tuesday. "While this proposition carries tremendous value for patients and society, it could represent a challenge for genome medicine developers looking for sustained cash flow."

Richter cited Gilead Sciences' treatments for hepatitis C, which achieved cure rates of more than 90 percent. The company's U.S. sales for these hepatitis C treatments peaked at $12.5 billion in 2015, but have been falling ever since. Goldman estimates the U.S. sales for these treatments will be less than $4 billion this year, according to a table in the report.

"GILD is a case in point, where the success of its hepatitis C franchise has gradually exhausted the available pool of treatable patients," the analyst wrote. "In the case of infectious diseases such as hepatitis C, curing existing patients also decreases the number of carriers able to transmit the virus to new patients, thus the incident pool also declines … Where an incident pool remains stable (eg, in cancer) the potential for a cure poses less risk to the sustainability of a franchise."

"Solution 3: Constant innovation and portfolio expansion: There are hundreds of inherited retinal diseases (genetics forms of blindness) … Pace of innovation will also play a role as future programs can offset the declining revenue trajectory of prior assets."